Satomura 2005.
| Study characteristics | ||
| Methods | RCT. Randomisation was achieved by simple computer‐generated random digit. Allocation was concealed using sealed, opaque envelopes. Not clear if there was a central randomisation centre. Post hoc exchange of envelopes was prevented by writing both the name of each participant and the number on the envelope he/she drew before breaking the seal. Participants were not blinded to the intervention; however, disease incidence was determined by 1 study physician who was not informed of the results of assignment. Analysis was done based on the intention‐to‐treat principle. The study targeted community healthcare all over Japan and was conducted between December 2002 and March 2003 for a follow‐up period of 60 days. | |
| Participants | 387 participants at 18 sites were recruited, 384 were included in the analysis: water gargling (N = 122), povidone‐iodine gargling (N = 132), and control (N = 130). Follow‐up was completed on 338 participants. Attrition was fully explained for URTI analysis; however, 2 participants were not accounted for in the ILI analysis. 46 participants did not complete the follow‐up due to either discontinuation of diary use (n = 9) or contracting ILI (n = 37). Of the 37 participants with ILI, 11 were in the povidone‐iodine group, 12 in the water group, and 14 in the control group. Analysis was performed on 35 participants (Kitamura 2007 [Kitamura 2007]). |
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| Interventions | Participants were randomised to 1 of the following: water gargling, n = 122 (20 mL of water for about 15 seconds 3 times consecutively, at least 3 times a day); povidone‐iodine gargling, n = 133 (20 mL of 15 to 30 times diluted 7% povidone‐iodine (as indicated by the manufacturer) in the same way as water gargling); and control, n = 132 (retain their previous gargling habits). All groups were asked to fill a daily gargling diary (standardised form to record: gargling habits, hand‐washing, and influenza complaints). The frequency of gargling in the water group was higher (3.6); the frequency of hand‐washing was similar amongst the 3 groups. URTI symptom was classified according to Jackson methods. Diary recording was continued throughout the follow‐up period and for 1 week after the onset of URTI. ILI was reported separately. See Table 4 for details. | |
| Outcomes | Laboratory: none
Effectiveness: Primary outcome: incidence of first URTI. Index cases were defined as all of the following conditions:
Secondary outcome: severity of URTI of the incident cases was assessed by grading each symptom during the initial 7 days after the onset of URTI in numeric scores: none = 0, mild = 1, moderate = 2, and severe = 3 ILI was defined as both developing a fever of 38 °C or higher and worsening arthralgia in addition to some respiratory symptoms (Kitamura 2007). Safety: no harm was reported. However, 2 participants in the povidone‐iodine group switched to water gargling (analysed in their assignment group). |
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| Notes | The authors concluded that simple water gargling is effective in preventing URTIs amongst healthy people. However, no statistically significant difference was observed against ILIs.
The study was well‐conducted; blinding would have added to the validity of the results. In addition, the study was not powered enough to detect a statistically significant preventative effect against ILI.
The study demonstrates that in addition to hand‐washing, simple gargling even with water can reduce URTI, but not ILI. However, during periods of endemic influenza, multiple inexpensive and simple modalities (hand‐washing, masks, gargling) can be utilised together to reduce infection and transmission.
Overall, the reporting of the 2 combined studies together is highly confusing. In the first study (Satomura 2005), the main outcome is URTI defined as fever and arthralgia. The second study (which is a presentation of further data from the 2005 publication in the guise of a short report) introduces the outcome ILI with a definition similar to that of URTI in the first study but referring to the earlier outcome as common cold. Also of note is reporting of significance without confidence intervals. Overall, this potentially important study should be repeated with a larger denominator.
Unclear risk of bias because of confused reporting and absence of double‐blinding. Partial financial support was provided by the Suzuken Memorial Foundation (2002) and Uehara Memorial Foundation (2003) (trial registry, ISRCTN67680497). No financial conflict of interest was reported by the authors of this paper. |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Quote: "Group assignment was based on simple computer‐generated random digits..." |
| Allocation concealment (selection bias) | Low risk | Quote: "By an individual drawing of sealed opaque envelopes, subjects were randomly assigned to the following three groups" Quote: "allocation was completely concealed from study administrators" |
| Blinding of participants and personnel (performance bias) All outcomes | High risk | Not blinded |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | Quote: "To prevent post hoc exchange of the envelopes, local administrators wrote down both the name of each subject and the number on the envelope he/she drew before breaking the seal." |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | 338 of 385 randomised followed up; reasons reported. |
| Selective reporting (reporting bias) | Unclear risk | Confusing reporting |